Plasmacytomas can be induced in 60% of BALB/c mice by the intraperitoneal injection of mineral oils. The induction procedure requires a conventional closed facility in which mice can be maintained in good health for 1 year. The primary effect of mineral oil is to induce the formation of a chronic granulomatous tissue. One effect of the work is to identify the specific cells and their products in this pathological microenvironment that influence plasmacytoma development. Most inbred strains of mice do not develop plasma cytomas, thus the BALB/c strain has a special genetic predisposition. Identification of specific genes and the functions they govern which determine susceptibility, is one approach to identifying critical factors in tumor development. We are actively pursuing this by a genetic analysis of BALB/c sublines and BALB/c congenic mice. Ninety-six percent of BALB/c plasmacytomas have non-random translocations involving chromosome 15 near the location of the oncogene. A focus of our research is to determine the role of the myc oncogene product in plasmacytoma physiology. Essential to this work is the need to develop monoclonal antibodies to myc gene products. Studies continue on the structure of the kappa and lambda Ig light chain loci in the mouse.